PROJECT SUMMARY/ABSTRACT The National Institute of Health report Diabetes in America (2018) noted that 39.5% of adults with diabetes are aged ? 65 years, and the prevalence of diabetes in older adults is dramatically increasing. Management of diabetes in older adults in nursing homes is challenging due to this population having heterogeneous comorbid medical conditions, and associated medications, many of which are contraindicated for common antidiabetic drugs. Intensive diabetes management in older adults is associated with an increased risk of hypoglycemia. Drug induced hypoglycemia is the 3rd most common adverse drug event among hospitalized Medicare beneficiaries. Hypoglycemia is experienced by 18% to 40% of nursing home residents. There is a lack of observational or clinical evidence pertaining to antidiabetic treatments in long-term care nursing home residents, despite this population being at high risk for diabetes, diabetes-related complications, and adverse effects of antidiabetic drugs. The American Diabetes Association?s consensus report on diabetes in older adults noted that ?There are essentially no directly applicable clinical trial data on glucose control for large segments of the older diabetic patient population.? Furthermore, there are few real-world studies of antidiabetic treatments in nursing home residents. In recognition of this knowledge gap in this high-risk population, the Diabetes Mellitus Interagency Coordinating Committee, as reported in the NIDDK Recent Advances & Emerging Opportunities (2019), issued a call for studies that increase our understanding of diabetes treatments in long-term care settings, with a particular emphasis on the need to understand the impact of cognitive and functional impairments, multimorbidity, polypharmacy, and risk of hypoglycemia. These priorities are central to our proposed scope of research. Using the Federally-mandated Minimum Data Set 3.0, linked to Medicare Part A and D claims, the aims are to: 1) characterize antidiabetic treatment practices among nursing home residents; 2) identify and describe clinically relevant phenotypes of diabetic nursing home residents based on patterns of cognitive/functional impairments, comorbidities, and treatment procedures/medications, and 3) estimate the occurrence of hospitalizations (overall, hypoglycemia-related, and hypoglycemia-specific) by propensity- matched patterns of antidiabetic treatments, across resident phenotypes. We hypothesize that risks associated with antidiabetic treatments will be heterogeneous across resident phenotypes. We anticipate that the phenotypic approach we propose will serve as a foundation for future work to conduct phenotypic-specific comparative effectiveness research in support of evidence-based personalized antidiabetic treatment recommendations.